Novel Synthesis and Properties of Multi-Phase Silicon Nitride-Based Structural Ceramics
Abstract
Structural ceramics for use in extreme, aerospace environments must meet stringent requirements and possess a broad suite of properties. The current study is being undertaken to show that multi-phase Si2ON2/Si3N4/SiO2/BN can be created using a novel two-step processing technique. In step one, nitridation in a tube furnace at approximately 1400oC is expected to turn Si, SiO2 and BN powders into #-Si3N4 and then #-Si3N4, while maintaining BN in the matrix. We will optimize the nitridation parameters and then compare and contrast the nitridation of Si3N4 from silicon powder versus silica powders. In step two, calcining the product in a gas pressure sintering furnace will be used to form Si2ON2, which has improved mechanical properties due to elongated grains and has also been predicted to have a reduced dielectric constant. The microstructural details associated with the Si2ON2 nucleation and growth during calcination are not well understood and will a major focus of the proposed study.Detailed phase analysis and microstructural observations will involve x-ray diffraction, scanning electron microscopy (SEM) with energy dispersive analysis (EDS) and orientation mapping (EBSD), and where warranted energy-filtered scanning transmission electron microscopy (TEM and STEM). These observations will be used to elucidate and optimize the formation of Si2ON2 and the attendant mechanical properties of the resultant multi-phase ceramic. In addition to the Si2ON2, the plate-like BN grains are expected to further improve the toughness of the overall composite. Moreover, processing the multi-phase ceramic in this manner facilitates net-near shape processing, eliminating the need for expensive and time consuming high-pressure hot isostatic pressing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2023
- Source ID
- N000142312764
Entities
People
- Kevin Hemker
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy